Plug-switch.



T. E. GAMBRELL.

PLUG SWITCH.

APPLIGATION FILED Nov.1a, 1913.

1,092,037. Patented Mar. 31, 1914,

Finca.

THOMAS EDWARD GAMBRELL, 0F LONDON, ENGLAND.

PLUG-SWITCH.

resaca?.

To all whom it may concern.'

Be it known that I, THOMAS EDWARD GAMBRELL, a `subject of the King ofGreat Britain, residing at London, England, have invented new and usefulImprovements in 4Plug` witches, of which the following is aspecification.

This invention relates to an improved switch of the plug type applicablefor use in connection with resistance boxes, `Wheat stone bridges,switchboards, contact makers and breakers and the like.

In the plug switches heretofore generally employed, e. g. on resistanceboxes, a conical plug has been forced into a socket formed by theadjacent shaped end surfaces of two blocks mounted on the ebonite top ofthe resistance box.4 I n this arrangement, the blocks themselves aremoved slightly during the insertion of the plug between them, so thatthere is a liability of the plug contacts at the other end of saidblocks being disturbed and the contact resistances altered.

According to the present invention, in order to prevent disturbance ofadjacent plug contacts and to reduce the contact resistance between thecoacting surfaces of the switch, I make the Xed part of the switch inthe form of pieces of metal arranged side by side and insulated fromeach other, the outer sides of said pieces of metal being shaped to formpart of a conical surface adapted to fit a correspondingly shaped1conducting surface in a cap, sleeve or ring, hereinafter referred to asa cap. The inner sides of said pieces of metal are preferably shaped toform part of a cylindrical surface adapted to fit around a pin,preferably of metal, secured concentrically in said cap. By thisarrangement the lateral forces on the xed contact pieces are balancedand much larger contact surfaces can be obtained.

In the accompanying drawings, I have shown how my said invention can beconveniently and advantageously carried into practice.

In these drawings: Figure 1 is a side elevation of partof resistance boxhaving my improved switches applied thereto, one of said switches beingshown in elevation and the other in section, and Fig. 2 is a planthereof, showing one switch with the cap on vand the other'with the capoft'. Fig. 3 ,is a

vertical central section and Fig. 4 a trans- Speoicaton of LettersPatent. I Pwgmed www, 319 9114,

Application led November 13, 1918.l SerialNo. 800,855.

verse section on the line, m, Fig. 3, showmg a modification.

a is an ebonite or other suitable slab forml ing a top to aresistance-box.

5, c; l), c, are pairs of conductors, the lower parts or bases d, d ofwhich are secured to the slab a. in any suitable known manner, forexample by means of steady pins (not shown), screwed pins e, c and nutsf, f and the upper parts of which are shaped to form parts of a cone gto lit the correspondingly-shaped interior of a metal cap k. Thejuxtaposed` faces of the conductors b, c are shaped to form parts of acylindrical surface y' adapted to t around a metal pin k securedconcentrically in the cap h. The conductors b, c are arranged at asuitable distance apart to provide eiicient air insulation. Similarly aspace m is provided between the bases d, d to facilitate cleaning oftheinsulating surface of the slab a.

. It will be seen that when the cap L is placed on the conical surface gof the conductors b, c the said conductors will be supported internallyby the pin la and thus lateral movement thereof will be prevented. Atthe same time the engaging surfacesvg, g may be made of any requiredsize to reduce the contact-resistance to any desired value. Moreover afurther reduction of the contact-resistance is obtained by theengagement of the surfaces j, j with the surface ofv the pin la. v

In the modification shown in Figs. 3 and 4t the cap l1. is provided onits exterior, adjacent to its open end, with a pair ofdiametrically-opposite lugs which are provided with segmentalscrew-threads n. When the cap lz. is applied the lugs may be passed downthe space o between the bases d', al' and when the cap h is turned thethreads n will engage with screw-threadsp on said bases d', d in orderto hold the cap k tightly on the conductors b, c fol-'example in caseswhere the switch is subjected to vibration. In some cases moreover thescrewthreads n, p can be replaced by Vone or more pins xed to the basesd, d and engaging with a corresponding spiral slot or slots in the cap,so that when the cap is turned in one direction the cap is drawn downtightly on to the conductors 5, c.

If desired a screw-thread can be arranged on the pin 7c and engage withcorresponding screw-threads on the adjacent surfaces of the conductorsb, o instead of arranging the 'l screw-threads 'as shown in Figs. 3 and4.'

What I-clairn is 1 A plug switch comprisin fixed conductors arranged ata suita le distance apart and insulated from each other and having theirouter surfaces shaped to form parts of a conical surface, and a caphaving an interior conducting surface shaped to`iton to saidconductors.l

2. A plug-switch comprisin xed conductors arranged at a suita ledistance apart and insulated from cach other, said conductors havingtheirVv outer surfaces shaped to form parts of a conical surface 15 andvtheir inner surfaces shaped to form parts of a cylindrical surface, lacap havingI an interior conducting surface and a plug mountedconcentrically in said cap and adapted to lit the innerv surfaces ofsaid 20 fixed conductors.

n THOMAS EDWARD GAMBRELL.

Witnesses:

JOHN T. KNoWLEs, H. CECIL BLAKE.

